Extractor Fans
Axial fans can either be mounted directly into a window or using a short length of ducting into an exterior wall http://www.simplifydiy.com/electrical/extractor-fans
Identifying And Dealing With Subsidence & Heave
However if several cracks suddenly appear in exterior brickwork interior plasterwork or around door and window frames you should investigate further http://www.simplifydiy.com/walls-and-ceilings/subsidence
Door Security
Home insurance companies and the police recommend that exterior doors are fitted with a http://www.simplifydiy.com/windows-and-doors/doors/door-security